1. Field of the Invention
The present invention relates to a microwave transistor mounting structure and particularly to a microwave transistor mounting structure in which a microwave transistor can be easily mounted and a stable grounding effect can be obtained.
2. Description of Prior Art
Recently, communication networks have been remarkably developed, a satellite communication system being one of such networks. For such satellite communication, frequencies in GH.sub.z band are used and G.sub.a A.sub.s (gallium arsenic) FETs or the like have begun to be used as signal amplifying elements in such a GH.sub.z frequency band communication. In the frequencies within the microwave frequency band (GH.sub.z frequency band) or in the higher frequency band, the inductance provided to a terminal per se, which extends to a grounded point, of a microwave transistor such as a G.sub.a A.sub.s FET or the like can not disregarded, and problems such as reduction in gain of the microwave transistor, deterioration in negative feedback, instability (positive feedback), etc., are caused. Accordingly, as to a microwave transistor, it is necessary to ground effectively at a minimum distance.
In the conventional mounting structure of the kind as described above, it has been necessary to perform bending in the manufacture to a ground terminal of a microwave transistor such as a G.sub.a A.sub.s FET or the like. For example, in FIGS. 1 and 2 showing a conventional microwave transistor mounting structure, a microwave transistor 1 such as a G.sub.a A.sub.s FET (gallium arsenic field effect transistor) or the like is provided with four terminals 1a, 1b, 1c, and 1d. The grounding terminals 1b and 1d have been subject to bending at their intermediate portion. Reference numeral 2 designates an alumina substrate or a circuit substrate of a copper clad laminated plate or the like, and 3 designates a metal chassis. The microwave transistor 1 is disposed on the substrate 2, with the terminal 1a and 1c connected to the substrate 2 by soldering or the like and with the terminals 1b and 1d grounded onto the chassis 3. Reference numeral 4 designates solder.
In such a conventional structure, however, the inductance inherently provided to the gronding terminals 1b and 1d per se can not be neglected and it is difficult to obtain sufficient performance of the microwave transistor. Further, it is necessary to perform bending to the grounding terminals 1b and 1d, and it is required to divide the substrate 2, which is primarily one piece, into two portions. Furthermore, it is required to mount the microwave transistor 1 at the later step. Thus, not only there was disadvantageous in assembling workability but, as described above, the grounding effect is not always good because the grounding terminals were elongated due to bending.
There is another example of the conventional structure, in which a microwave transistor has its ground terminals connected through holes in a substrate to rear electrodes, whereby they can be grounded onto a metal chassis. Although this structure is advantageous in view of assembling workability in comparison with the above-mentioned prior art example, the inductance is large similarly to the above-mentioned example and therefore it is difficult to use this example structure in the microwave frequency band.